#include <stdio.h>

int gcd(int a, int b);
int gcdIter(int a, int b);

int main(void) {
  int a,b;

  printf("\nGreatest common divisor\n");
  printf("\nEnter the first number: \n");
  scanf("%i",&a);
  printf("\nEnter the second number: \n");
  scanf("%i",&b);
  
  printf("\nGreatest common divisor by recursion: %i\n",gcd(a,b));
  printf("\nGreatest common divisor by iteration: %i\n",gcdIter(a,b));

  return 0;
}


int gcd(int a, int b) {
  int r; 

  if ((r = a % b) == 0) {
    return b;
  } else {
    return gcd(b,r);
  }
}


int gcdIter(int a, int b) {
  int minVal, maxVal, i; 

  if (a > b) {
    maxVal = a;
    minVal = b;
  } else {
    maxVal = b;
    minVal = a;
  } 

  i = minVal;
  while (i >= 1) {
    if (((maxVal % i) == 0) && ((minVal % i) == 0)) {
      return i;
    } else {
      i--;
    }
  }
  return i;
}